Place the double cream and milk into a pan and bring to the boil. Remove from the heat and stir in the chocolate until melted. Set aside to cool. In a bowl, beat together the egg yolks and sugar until smooth. Stir into the cooled chocolate-cream mixture. Stir until smooth. Dip the Brioshe slices into the chocolate sauce and then layer them in the oven-proof dish, overlapping the slices as you go. Place the dish into a roasting pan and fill the roasting pan to 2/3 full with boiling water. Bake for 25 - 30 minutes until the sauce has thickened.

Bring cream, liqueur, sugar, and vanilla to boil in heavy medium saucepan over medium-high heat, stirring frequently. Mix cornstarch and 10mls water in small bowl to blend; whisk into cream mixture. Boil until sauce thickens, stirring constantly, about 3 minutes. Cool, then cover and refrigerate until cold, about 2 hours. (Can be made 3 days ahead. Keep refrigerated.)